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[222.167.244.67]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2eae6b76df7sm15602385ad.14.2026.10.27.15.57.13 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Tue, 27 Oct 2026 15:57:17 -0700 (PDT) From: Guoshuai Yang To: Steffen Klassert , Herbert Xu , Sabrina Dubroca Cc: "David S . Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , David Ahern , Guoshuai Yang , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH net v4] xfrm: esp: reset outer TCP GSO metadata on espintcp input Date: Wed, 28 Oct 2026 06:57:10 +0800 Message-ID: <20261027225710.51832-1-yangguoshuai@gmail.com> X-Mailer: git-send-email 2.54.0 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit When ESP packets are received over TCP (RFC 8229 espintcp), strparser slices individual length-prefixed ESP records from the outer TCP stream by cloning the incoming TCP skb(s) in __strp_recv(). If the outer TCP skb was GRO-coalesced before reaching strparser, its skb_shinfo carries the outer TCP stream's GSO metadata (gso_size, gso_segs, and gso_type). When an ESP record spans two outer TCP segments, strparser chains the spillover clone onto skb_shinfo(head)->frag_list. Subsequently in esp_input() and esp6_input(), skb_cow_data() unshares the head skb via pskb_expand_head() (preserving the outer TCP gso_size and gso_type in the new private skb_shinfo) and calls skb_copy() on each cloned frag_list member, which copies the outer TCP GSO fields via skb_copy_header() onto a linear frag_list child skb allocated from slab with head_frag == 0. Furthermore, on kernels with TCP fraglist GRO support, if an outer TCP GRO aggregate carrying SKB_GSO_FRAGLIST reaches the espintcp socket unsegmented (for example, when rx-gro-list is enabled on a device in an outer netns where tcp4/6_check_fraglist_gro() finds no local socket and the aggregate is forwarded across a NETIF_F_GSO_FRAGLIST-capable veth device into the netns hosting the espintcp socket) and is chained onto skb_shinfo(head)->frag_list by __strp_recv(), skb_cow_data() invokes skb_copy() / skb_copy_expand() on that frag_list member and hits WARN_ON_ONCE(skb_shinfo(skb)->gso_type & SKB_GSO_FRAGLIST), failing with -ENOMEM before decryption even begins. (On older stable trees without TCP fraglist GRO, the pre-pass is a no-op.) After ESP decryption and header removal, the resulting single inner packet still has skb_is_gso(skb) == true with the stale outer TCP gso_size, while skb_headlen(head_skb) is now smaller than that gso_size due to stripping the outer framing and ESP header. When this packet passes through gro_cells_receive() (which flushes frag_list packets via GRO_NORMAL without resetting gso_size) and is forwarded, validate_xmit_skb() invokes tcp_gso_segment() -> skb_segment(). Because head_skb is shorter than the stale gso_size and SKB_GSO_DODGY is not set, skb_segment() attempts to map the slab-backed frag_list member as a scatter-gather page fragment where list_skb->head_frag == 0. On current mainline kernels, skb_segment() triggers DEBUG_NET_WARN_ON_ONCE(1) and fails with -EINVAL, causing validate_xmit_skb() to drop all multi-segment espintcp packets. On stable kernels prior to the removal of BUG_ON(!list_skb->head_frag) in skb_segment() (such as 6.12.94 where this trace was captured), it crashes the kernel: Internal error: Oops - undefined instruction: 0 [#1] SMP ARM PC is at skb_segment+0x574/0xd20 LR is at skb_segment+0x884/0xd20 Call trace: skb_segment from tcp_gso_segment tcp_gso_segment from inet_gso_segment inet_gso_segment from skb_mac_gso_segment skb_mac_gso_segment from __skb_gso_segment __skb_gso_segment from validate_xmit_skb validate_xmit_skb from __dev_queue_xmit __dev_queue_xmit from ip_finish_output2 ip_finish_output2 from ip_output ip_output from ip_sublist_rcv_finish ip_sublist_rcv_finish from ip_sublist_rcv ip_list_rcv from __netif_receive_skb_list_core __netif_receive_skb_list_core from __netif_receive_skb_list __netif_receive_skb_list from gro_normal_list gro_normal_list from gro_cell_poll Similarly, if a decrypted inner packet with a frag_list later takes the ip_do_fragment() frag_list fast path, each detached frag_list member is transmitted as a standalone IP fragment and would still carry the stale outer TCP GSO state when reaching validate_xmit_skb(). And even when an ESP record does not have a frag_list, leaving the stale outer TCP gso_size on the decrypted inner skb prevents dev_gro_receive() from initializing gso_size to the inner packet's skb_gro_len(). We cannot reset GSO state earlier in espintcp_rcv() / handle_esp() because the skb may still be a clone sharing skb_shinfo with the outer TCP skb held by strparser. Instead, in esp_input() and esp6_input(): 1. Prior to skb_cow_data(), unshare/unclone and reset GSO metadata on any frag_list member carrying SKB_GSO_FRAGLIST (unsharing any shared predecessor frag_list members along the walk) so skb_copy() / skb_copy_expand() inside skb_cow_data() does not hit WARN_ON_ONCE() and drop the packet. 2. At skip_cow, where the head skb and all frag_list members are guaranteed to be uncloned with private skb_shinfo, call skb_gso_reset() on both the head skb and each skb_walk_frags() member. Fixes: e27cca96cd68 ("xfrm: add espintcp (RFC 8229)") Cc: stable@vger.kernel.org Signed-off-by: Guoshuai Yang --- v4: - In esp_reset_espintcp_fraglist_gso(), unshare any shared frag_list member before checking SKB_GSO_FRAGLIST so *fragp = frag never writes through a shared predecessor's ->next pointer. - Clarify in the commit message that on current mainline kernels skb_segment() triggers DEBUG_NET_WARN_ON_ONCE(1) and returns -EINVAL (dropping the packet in validate_xmit_skb()), whereas the BUG_ON() oops trace was captured on 6.12.94 LTS. - Clarify the cross-netns veth forwarding topology required for TCP fraglist GRO (SKB_GSO_FRAGLIST) aggregates to reach esp_input() unsegmented. - Link to v3: https://lore.kernel.org/netdev/20261023065311.65031-1-yangguoshuai@gmail.com/ v3: - Unshare/unclone and reset GSO metadata on any frag_list member carrying SKB_GSO_FRAGLIST before skb_cow_data() so skb_copy() / skb_copy_expand() does not hit WARN_ON_ONCE(SKB_GSO_FRAGLIST) and return -ENOMEM. - Move the shared espintcp GSO reset helpers into include/net/esp.h. - Link to v2: https://lore.kernel.org/netdev/20261020030450.7170-1-yangguoshuai@gmail.com/ v2: - Also call skb_gso_reset() on each skb_walk_frags() member at skip_cow in esp_input() and esp6_input() so detached frag_list members on the ip_do_fragment() fast path do not retain stale outer TCP GSO state. - Specify target tree 'net' in subject prefix. - Link to v1: https://lore.kernel.org/netdev/20261018005218.53267-1-yangguoshuai@gmail.com/ include/net/esp.h | 51 +++++++++++++++++++++++++++++++++++++++++++++++ net/ipv4/esp4.c | 9 +++++++++ net/ipv6/esp6.c | 9 +++++++++ 3 files changed, 69 insertions(+) diff --git a/include/net/esp.h b/include/net/esp.h index 3229507..83c75ef 100644 --- a/include/net/esp.h +++ b/include/net/esp.h @@ -28,6 +28,57 @@ static inline void esp_output_fill_trailer(u8 *tail, int tfclen, int plen, __u8 tail[plen - 1] = proto; } +static inline int esp_reset_espintcp_fraglist_gso(struct sk_buff *skb) +{ + struct sk_buff **fragp; + struct sk_buff *frag; + + skb_walk_frags(skb, frag) { + if (skb_shinfo(frag)->gso_type & SKB_GSO_FRAGLIST) + break; + } + if (!frag) + return 0; + + if (skb_unclone(skb, GFP_ATOMIC)) + return -ENOMEM; + + for (fragp = &skb_shinfo(skb)->frag_list; (frag = *fragp); + fragp = &frag->next) { + if (skb_shared(frag)) { + struct sk_buff *nfrag; + + nfrag = skb_clone(frag, GFP_ATOMIC); + if (!nfrag) + return -ENOMEM; + + nfrag->next = frag->next; + consume_skb(frag); + frag = nfrag; + *fragp = frag; + } + + if (!(skb_shinfo(frag)->gso_type & SKB_GSO_FRAGLIST)) + continue; + + if (skb_unclone(frag, GFP_ATOMIC)) + return -ENOMEM; + + skb_gso_reset(frag); + } + + return 0; +} + +static inline void esp_reset_espintcp_gso(struct sk_buff *skb) +{ + struct sk_buff *iter; + + skb_gso_reset(skb); + skb_walk_frags(skb, iter) + skb_gso_reset(iter); +} + struct esp_info { struct ip_esp_hdr *esph; __be64 seqno; diff --git a/net/ipv4/esp4.c b/net/ipv4/esp4.c index e76db58..92980cd 100644 --- a/net/ipv4/esp4.c +++ b/net/ipv4/esp4.c @@ -893,6 +893,12 @@ static int esp_input(struct xfrm_state *x, struct sk_buff *skb) } } + if (x->encap && x->encap->encap_type == TCP_ENCAP_ESPINTCP) { + err = esp_reset_espintcp_fraglist_gso(skb); + if (err) + goto out; + } + err = skb_cow_data(skb, 0, &trailer); if (err < 0) goto out; @@ -900,6 +906,9 @@ static int esp_input(struct xfrm_state *x, struct sk_buff *skb) nfrags = err; skip_cow: + if (x->encap && x->encap->encap_type == TCP_ENCAP_ESPINTCP) + esp_reset_espintcp_gso(skb); + err = -ENOMEM; tmp = esp_alloc_tmp(aead, nfrags, seqhilen); if (!tmp) diff --git a/net/ipv6/esp6.c b/net/ipv6/esp6.c index b1c9b36..65470d3 100644 --- a/net/ipv6/esp6.c +++ b/net/ipv6/esp6.c @@ -936,6 +936,12 @@ static int esp6_input(struct xfrm_state *x, struct sk_buff *skb) } } + if (x->encap && x->encap->encap_type == TCP_ENCAP_ESPINTCP) { + ret = esp_reset_espintcp_fraglist_gso(skb); + if (ret) + goto out; + } + nfrags = skb_cow_data(skb, 0, &trailer); if (nfrags < 0) { ret = -EINVAL; @@ -943,6 +949,9 @@ static int esp6_input(struct xfrm_state *x, struct sk_buff *skb) } skip_cow: + if (x->encap && x->encap->encap_type == TCP_ENCAP_ESPINTCP) + esp_reset_espintcp_gso(skb); + ret = -ENOMEM; tmp = esp_alloc_tmp(aead, nfrags, seqhilen); if (!tmp) -- 2.54.0 (Apple Git-157)